What is the difference between EMI and EMC?

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- everything RF

May 16, 2024

Electromagnetic Interference (EMI) and Electromagnetic Compatibility (EMC) are two common, but very different topics that we talk about when discussing regulatory testing and compliance of electronic components and systems. In short, EMI refers to the disturbance generated by an external source that affects an electrical circuit through electromagnetic induction, coupling or conduction. It disturbs the normal operation of electronic devices in its sorroundings, causing them to malfunction or produce unwanted behavior. EMC, however, is an electronic device or system's ability to operate without malfunctioning in the presence of electromagnetic interference. Let’s discuss EMI and EMC separately.

EMC vs EMI - What is the difference?

Electromagnetic Interference (EMI)

Electromagnetic interference (EMI) refers to the disturbance caused by an electronic device or system while it is operating. These disturbances are unwanted electromagnetic signals that are emitted by the device while it is operating. As a result, EMI from a device can degrade the performance of other electronic components or systems in its surroundings. This disturbance usually manifests as noise, which leads to signal degradation and can result in a device malfunctioning. This type of EMI is called man-made EMI. Another form of EMI can be generated from natural sources, these include events like solar flares, lightning, and auroras that result in the generation of unwanted electromagnetic signals that can impact the performance of electronic devices and systems.

EMI has diverse effects on the performance of electronic systems, It can result in signal degradation, causing distortion or loss of transmitted information. In some cases, it may disrupt normal operations to a point where extreme malfunction or complete failure of a device can occur. Therefore, it becomes extremely important to follow the practices that can help minimize or mitigate EMI. This includes shielding sensitive components with metallic enclosures and ensuring proper grounding to protect the electronics inside. Twisted pair cables are also used to cancel out the effects of interference. Additionally, adherence to regulatory standards for electromagnetic compatibility further helps in mitigating the effects of EMI.

Electromagnetic Compatibility (EMC)

Electromagnetic compatibility (EMC) refers to the ability of electronic devices to function properly in a given electromagnetic environment without causing excessive electromagnetic interference (EMI) to other devices in the vicinity. It ensures that electronic systems can operate without disrupting each other or being disrupted by external electromagnetic signals. 

EMC has two parts - Emission of electromagnetic waves and immunity against them. Emission deals with the unintentional generation of electromagnetic energy by a device and its transmission in the environment. These emissions should be kept within acceptable limits to prevent interference with other nearby devices. Immunity is the ability of the device to operate as intended despite being exposed to electromagnetic disturbances from external sources. Electronic devices need to be designed in such a way that they’re immune to such disturbances to maintain their functionality and reliability. This can be achieved by following various strategies like proper design practices, shielding, filtering, grounding, and compliance testing.  

In conclusion, Electromagnetic compatibility (EMC) and interference (EMI) are both extremely important design considerations. Failing to consider them in the initial stages of product development can result in the time-consuming and costly need to redesign the product at a later stage to meet EMC/EMI specification tests and prevent product failure or safety risks.

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